A common practice in racing applications is file fitting piston ring end gaps. Most Hastings Performance
Rings are available in file fit (+ .005”) oversizes.
Today’s performance piston designs are moving the top compression ring higher for optimal performance.
This creates even higher operating temperatures, therefore requiring a larger top compression ring end
Gap. Also, improved thermal efficiency of a hypereutectic piston alloy keeps more usable heat in the combustion chamber, with less heat moving down through the piston onto the piston skirt and into the oil.
Use the chart below to determine the minimum ring end gap. Multiply bore size x ring end gap factor.
Example: For a naturally aspirated street engine using a cast piston with 4.000″ bore, the top ring end gap would be 4.000 x .004″ = .016″. The second ring end gap would be 4.000 x .0045″ = .018″. The oil rails should always have a minimum end gap of .015″.
Safe, Recommended Automotive Compression Ring Gap Clearances
Failure to check ring end gap can result in severe engine damage. The above end gap recommendations are general guidelines. The final end gap suitable for the engine is the full responsibility of the engine builder